The purpose of this research project is to study the biosynthesis of collagen cross-linking and characterize lysyl oxidase, the enzyme catalyzing formation of the lysine derived aldehydes that form cross-links. Highly purified lysyl oxidase is incubated with a chick calvarium collagen substrate that has been labelled with radioactive amino acids in organ cultures. The products of the incubations are being characterized by either oxidation or reduction and then amino acids analysis. The cofactor requirements, substrate specificity and kinetic parameters of chick epiphyseal cartilage lysyl oxidase are also being studied. Research to date indicates that the enzyme has high activity for collagen fibrils, apparent Km of 9.5 x 10 to the minus 8th power but low activity for collagen monomers or peptides.